Concentration of simple aldehydes by sulfite-containing double-layer hydroxide minerals: Implications for biopoesis

Environmental conditions play an important role in conceptual studies of pr ebiotically relevant chemical reactions that could have led to functional b iomolecules. The necessary source compounds are likely to have been present in dilute solution, raising the question of how to achieve selective conce ntration and to reach activation. With the assumption of an initial 'RNA Wo rld', the questions of production, concentration, and interaction of aldehy des and aldehyde phosphates, potential precursors of sugar phosphates, come into the foreground. As a possible concentration process for simple. uncha rged aldehydes, we investigated their adduct formation with sulfite ion bou nd in the interlayer of positively charged expanding-sheet-structure double -layer hydroxide minerals. Minerals of this type, initially with chloride a s interlayer counter anion, have previously been shown to induce concentrat ion and subsequent aldolization of aldehyde phosphates to form tetrose, pen tose, and hexose phosphates. The reversible uptake of the simple aldehydes formaldehyde, glycolaldehyde, and glyceraldehyde by adduct formation with t he immobilized sulfite ions is characterized by equilibrium constants of K= 1.5, 9, and 11, respectively. This translates into an observable uptake at concentrations exceeding 50 mM.